ABSTRACT
Contaminated sediments become an issue when environmental or human risk is identified and navigational needs require that contaminated sediments be dredged from shipping channels. In the United States, 14 to 28 million cubic yards of sediments must be managed every year and decontamination is the necessary step before disposal or reuse as a secondary material.
Since the SO2/O2 system has been successfully applied to the destruction of cyanide in a safe and reliable manner, it is worthwhile to investigate its possible use for the remediation of contaminated sediments. It was found that the metal content of contaminated sediments decreased significantly after treatment in a NaOH solution sparged with the SO2/O2 mixture. In particular, metals like Cu, Cd, Pb and Cr were removed by this procedure. The efficiency of the process was function of the duration of the treatment, its temperature and the final pH. By increasing the temperature, the metal removal efficiency could be improved, with the exception of Cu. A final acidic pH produced higher metal recoveries than a basic pH. Under optimum conditions, a process run at 80 °C, for 120 minutes with a NaOH concentration of 0.5 M was able to remove 90% of Pb and Cr, and 70% of Cu. A treatment for 300 minutes, at 25 °C with a final pH equal to 1.5 completely removed Cd. Sedimentation tests indicated that the particle size distribution of the sediments changed after treatment with the appearance of a finer size; it can be postulated that organic compounds, binding these particles together, were destroyed during the treatment.
